1. Field of the Invention
The invention relates to a power semiconductor technique. More particularly, the invention relates to an edge terminal structure and a trench power metal oxide semiconductor field effect transistor.
2. Description of Related Art
A power semiconductor device is often applied to a switch mode power supply or other high-speed power switches. According to requirements of the power semiconductor device, an active area of the device needs to allow large current to pass through, and the terminal area of the device needs to withstand large breakdown voltage.
At present, several power semiconductor devices (e.g., the barrier Schottky diode) have been developed and employed. Since the breakdown voltage of the normal planar barrier Schottky diode is not high enough, a trench metal oxide semiconductor barrier Schottky (TMBS) diode shown in FIG. 1 has been developed recently.
With reference to FIG. 1, in the TMBS diode 10, an N− epitaxial layer 102 is formed on an N+ substrate 100, a plurality of trench gates 104 are formed in the N− epitaxial layer 102, and a gate oxide layer 106 is configured between the trench gates 104 and the N− epitaxial layer 102. A barrier Schottky metal layer 108 and an anode metal 110 are then deposited on a surface of the N− epitaxial layer 102 and surfaces of the trench gates 104.
FIG. 1 merely illustrates the structure of an active area, and how to design an edge terminal structure adapted to the TMBS diode 10 has become one of the key research topics in various fields. For instance, U.S. Pat. No. 6,309,929 and U.S. Pat. No. 6,396,090 have both disclosed similar concepts.
In addition to the TMBS diode, other power semiconductor devices such as a trench power metal oxide semiconductor field effect transistor (MOSFET), a trench insulated gate bipolar transistor (IGBT), etc. have also encountered the same issues.